The present invention relates to the field of equipment used both for rock-climbing and for suspending or fixing objects to a rock or concrete or other wall and relates more particularly to a removable anchoring bolt. The invention also relates to the field of hoisting heavy loads (girders, concrete blocks, etc.).
Anchoring devices designed to be anchored in holes drilled in solid materials constituted by rock or concrete are known from the state of the art. Certain of these devices present the drawback of being usable once only and of not being able to be removed after use. Furthermore, they can only be placed by means of fastening tools and are therefore difficult to use in the field of rock-climbing, load hoisting or whenever a wall has to be left devoid of any device.
Removable anchoring devices, of bolt type, able to be used to suspend objects on walls are also known from the state of the art. The advantage of such devices is to be able to be easily removed from the drilled holes which accommodate them to be placed in other drilled holes.
Such devices are in particular known from U.S. Pat. No. 3,861,636 and from Patent application FR 2,411,328.
A removable anchoring device for rock-climbing able to be removed from the wall after use is also known from Patent application WO 97/32631.
A cable anchoring, for rock-climbing, difficult to remove from the wall when it has been heavily stressed, is also known from U.S. Pat. No. 6,729,821.
Typically, removable anchoring devices of the bolt type are designed to each be engaged in a hole drilled in the wall and are each formed by a female body that is radially expandable in the drilled hole, receiving with axial sliding a male body in the form of a cylindrical shank provided at its distal end with a frustum-shaped expansion head compelled, by movement of the shank, to penetrate into the female body in order to dilate the latter. The relative axial movement of the male body with a view to dilating the female body results from the action of a flexible part, threaded onto the male body and fitted in compression between the female body and a rim of the proximal end of the male body. Due to the effect of its expansion, the female body is applied against the surface of the drilled hole, which makes a connection by adherence and secures the bolt in the drilled hole. To release the anchoring bolt, the user applies an axial force on the male body so that its head is at least partially disengaged from the female body. In this way, the link by obstacle is broken and the bolt can then be separated from the wall.
Usually the male body is equipped to receive loads, and has for this reason to have a sufficiently large cross-section to withstand the mechanical stresses generated by the latter.
The shank forming the male body of prior art devices, due to the design of the latter, presents a substantially smaller diameter than that of the hole to be drilled in the wall. For this reason, on account of the diameter constraint imposed for the shank, the female body and the drilled hole are thereby over-dimensioned. Furthermore to prevent the shank from adopting an oblique position in the hole due to the effect of the load, the female body has to be sufficiently long to present a support span, to the rear of its area subjected to expansion, ensuring coaxiality of the shank and of the drilled hole.